1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same.
2. Description of the Related Art
An interface trap produced by defects existing in the interface between a semiconductor and insulating film forming a MOS device has an influence on the electric character of the MOS device. For example, the interface trap can generate noise in the operation of a MOS transistor in a source follower circuit.
For example, Japanese Patent Laid-Open No. 7-122733 has disclosed a buried channel type MOS transistor having a channel formed in a position deeper than a p-type impurity region 8 formed in the surface portion of a semiconductor region. According to patent literature 1, this structure reduces the influence of noise caused by the interface trap.